It compiles at least, but I didn't get around to testing yet. Looking at the changes though, those changes shouldn't be more than cosmetic. That doesn't mean that the code I didn't touch will work
Looking at the number of deprecated warnings that continue to be thrown, I don't expect this to be a fix for more than a few months, until ffmpeg dances the jig again.

Once you open a bug, you can test that code and see if it actually works, then submit it as a patch, in the hope that this will get it revision-bumped in portage.

Edit: Just tried opening a SomaFM AAC stream with it, and while it's not the complete failure it was before without AAC support, it still only loads the metadata, and will not open the stream.
I'll leave fixing that as an exercise to the reader

So, I just tried, and that version compiles flawlessly.
Clearly the issue here is that while Squeezeslave is already a badly maintained piece of software, it is even worse cared for in the Portage tree.
Until further notice I would recommend manually building the 1.3, I suppose aac and wma are activated by default, as all of the configure is automatically done by the makefile.

I'll test it now, and get back to you and the bug report with my results ASAP.

Edit:

I still cannot get AAC streams from SomaFM to work, with this version. Haven't tried others or "local" files yet.

" Ignore the AAC and WMA decoders as I'm planning to rewrite them and they are not part of the official build anyway."

and since then there was no further mention of this feature, and a feature freeze for squeezeslave was announced in April of this year.
Apparently squeezelite is supposed to take over as a more fully featured alternative.

I think I tried squeezelite, before settling on squeezeslave, and it just didn't work at the time.

Anyway, it doesn't look too good for aac support, it's definitely not supported in the latest build.

Edit: I think the issue with sqeezelite was its inability to run as a service on my machine.
It does play AAC when started attached to a shell though.
Auto-discovery of LMS also fails.